Enamel matrix proteins such as those present in enamel matrix are best known as precursors of dental enamel. Enamel proteins and enamel matrix derivatives have previously been described in the patent literature to induce hard tissue formation (i.e. enamel formation, cf. U.S. Pat. No. 4,672,032 (Slavkin)) or binding between hard tissues (EP-B-0 337 967 and EP-B-0 263 086). In recent animal studies using enamel matrix proteins for regeneration of tooth attachment, it has been observed that the regeneration and healing progresses with minimal signs of epithelial interference. This is in contrast to all other regenerative therapies of the periodontium where epithelial downgrowth from the oral cavity into the lesion is a common complication. To investigate possible restrictive effects of enamel matrix proteins on epithelial cell growth, epithelial cells were cultured in the presence of enamel matrix proteins.